His name was later used for streets and places such as Hans Place, Hans Crescent, and Sloane Square in and around Chelsea, London - the area of his final residence - and also for Sir Hans Sloane Square in his birthplace in Ireland, Killyleagh.
Sloane was born on 16 April 1660 at Killyleagh in County Down, Ireland. He was the seventh son of Alexander Sloane (died 1666), agent for James Hamilton, second Viscount Clandeboye and later first Earl of Clanbrassil. Sloane's family had migrated from Ayrshire in Scotland, but settled in the north of Ireland under James I. His father died when he was six years old.
As a youth, Sloane collected objects of natural history and other curiosities. This led him to the study of medicine, which he went to London, where he studied botany, materia medica, surgery and pharmacy. His collecting habits made him useful to John Ray and Robert Boyle. After four years in London he travelled through France, spending some time at Paris and Montpellier, and stayed long enough at the University of Orange-Nassau to take his MD degree there in 1683. He returned to London with a considerable collection of plants and other curiosities, of which the former were sent to Ray and utilised by him for his History of Plants.
Sloane was elected to the Royal Society in 1685. At the same time, he attracted the notice of Thomas Sydenham, who gave him valuable introductions to practice. In 1687, he became a fellow of the College of Physicians, and the same year went to Jamaica aboard HMS Assistance as physician in the suite of the new Governor of Jamaica, the second Duke of Albemarle. Jamaica was fast emerging as a source of immense profit to British merchants based on the cultivation of sugar and other crops by the forced labor of West Africans—many from the Akan and other peoples of the regions which the English entitled the Gold and Slave Coasts.
However, Albemarle died in Jamaica the next year, so Sloane's visit lasted only fifteen months. During that time he noted about 800 new species of plants, which he catalogued in Latin in 1696; he later wrote of his visit in two lavishly illustrated folio volumes (1707–1725). He was the President of Royal College of Physicians and he became secretary to the Royal Society in 1693, and edited the Philosophical Transactions of the Royal Society for twenty years.